The invention relates to an electromagnetic actuator for operating a gas exchange valve of an internal combustion engine, wherein the actuator includes at least one electromagnet, which is arranged in a housing and acts on an armature.
DE 197 14 496 A1 discloses an electromagnetic actuator of this general type for actuating a gas exchange valve of an internal combustion engine. An opening magnet and a closing magnet which each have a magnet coil wound onto a coil core are arranged in an actuator housing. The magnets act on an armature adapted to move in the axial direction of the valve. Furthermore, the actuator includes a cooling structure having a cooling passage extending in the actuator housing. Bores in the actuator housing form the cooling passage. Cooling liquid can be conducted through the cooling passage without coming into direct contact with the magnet coils and the coil cores.
Furthermore, DE 196 28 860 A1 discloses an electromagnetic actuator for actuating a gas exchange valve of an internal combustion engine having a pivoting armature, which is mounted between two electromagnets in a manner such that it can pivot about an axis.
It is the object of the present invention to provide an improved actuator of this type.
In an electromagnetic actuator for actuating a gas exchange valve of an internal combustion engine, the actuator includes at least one electromagnet which is arranged in a housing and acts on an armature through which at least one passage extends transversely with respect to the direction of movement of the armature for conducting a coolant through the armature.
As the cooling fluid passage extends through the armature advantageous cooling of the armature can be achieved and heat can be removed from a core of the electromagnet via the armature. As a result, the degree of efficiency of the actuator can be increased. If an armature is guided displaceably in a translatory manner, the fluid may, for example, be conducted into the armature via a bearing of an armature tappet and via the armature tappet.
However, it is particularly advantageous for the armature to be designed as a pivoting armature and for the fluid to be fed in by way of a bearing point of the armature. With little structure outlay, the coolant can then be conducted through a short path into the armature and, in addition, a play-compensating element can be supplied in a particularly advantageous manner with a pressure medium via the passage in the armature, the play-compensating element being arranged, for example, between the armature and an armature stem or valve stem.
In a particular embodiment of the invention, the fluid is removed at a second bearing point of the armature. As a result, a large through-flow through the armature and good dissipation of heat can be achieved. In principle, however, the medium could also be removed at another point, for example a point on the armature, via a play-compensating element, etc.
If the armature is connected to a hollow pivoting spindle, the medium can be fed to the armature via the pivoting spindle in a structurally simple and cost-effective manner. If the medium is fed in via a first bearing point of the armature and the medium is removed via a second bearing point, it is advantageous if a partition is arranged between the bearing points of the hollow pivoting spindle, by which partition a direct flow through the pivoting spindle and a flow short circuit of the passage in the armature can be avoided. The partition can be formed integrally with the pivoting spindle or else as a separate component, which is inserted into the pivoting spindle. If the pivoting spindle is connected via the partition to a torsion spring, additional components, weight, outlay on installation and costs can be saved.
In another embodiment of the invention, the armature is mounted via at least one bearing bolt and the medium is fed into the armature through a passage in the bearing bolt. A pressure drop upstream of the passage can be avoided and a large through-flow can be achieved. With small pressure drops, a play-compensating element can be supplied with pressure medium via the armature. However, it is also possible to supply the medium to the passage via a bearing surface or else via a bearing surface of an anti-friction bearing, as a result of which the bearing surfaces can be advantageously lubricated by the medium at the same time. The medium can be formed by different substances which, for example, are designed primarily for transporting away heat or for lubrication. However, it is particularly advantageous if the medium is internal combustion engine oil, which can be used as pressure medium for a play-compensating element, for cooling and for lubricating and, which, in principle, is available in any internal combustion engine.
Preferably, the passage extends in a curved manner through the armature, as a result of which a large cooling surface and an advantageous dissipation of heat from the armature can be achieved with a small pressure drop. However, it is also possible for the passage to extend rectilinearly through the armature or to consist of a plurality of rectilinear sections.
Further advantages will become apparent from the following description of the invention on the basis of the accompanying drawings.